1988 Mercury 45 hp classic 50 idling probs & only 4000 rpms at WOT

[ugadawg187]

Not sure of the yr model yet i havent pulled the serial number to check but i believe its a mid to late 80's. It goes dead at idle unless you give it some throttle & its sluggish until you hit around 2500-3000rpm. I believe it prob needs a carb job but i wanted to check all the causes of this. Compression was said to check out at 100 on all four cylinders.

 

[verado7]

Re: Mercury 45 hp classic 50 idling probs

Re: Mercury 45 hp classic 50 idling probs

i have one of these motors - i'd suggest rebuilding the carbs first and fuel pump at the same time to rule out a fuel issue - besides they need to be done every 3 or 4 years - you can also check the trigger voltages with motor running use a regular voltmeter and check the black,violet,white , and brown trigger wires - you want 5volts minimum - then test resistance for 700- 1000 ohms - the trigger can cause the problems you describe and usually first thing i check when it wont idle on its own - of course you also need to rule out fuel and its cheap enough to do teh carbs and fuel pump anyway .

the trigger is what tells the pack to fire -low voltage here will affect normal idle - if you come up with low voltages - disconnect the trigger wires and retest with motor running - if voltage is good now -the switchbox is bad .

 

[ugadawg187]

Re: Mercury 45 hp classic 50 idling probs

Re: Mercury 45 hp classic 50 idling probs

wow thanks for the info maybe i should let a mechanic look at it as i dont feel to comfortable doing all that myself but i might try. Here is a pic of the motor just so everybody can see it.

 

[ugadawg187]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

Ok so i talked to a mechanic today & he said if it wasnt the carbs then it would more than likely be the stator. He said the trigger either works or it doesnt. Said theres no inbetween where it might half way work. With that said i guess the trigger is ruled out unless he's wrong. Also what should the rpms be on this motor at WOT? Im only hitting around 3800-4000 & only doing around 15mph which seems really slow for suach a small boat.

 

[verado7]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

thats not true - in fact i just replaced a trigger that only acted up at 4000 rpm and above - and at idle it only had 3 volts ( should have 5v) . trigger replaced - problem solved . dont buy into teh whole it either works or doesn't scenario - i've heard that one about every part of the ignition .

 

[SC1650]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

I have the next generation 40 HP Oil Injected unit (1993) and according to my manual 5500 is max RPM for my engine. I can get 6000 if I raise the engine but that is to much RPM to carry for a long period of time so I don't do it.

 

[shankforce]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

How does the mechanic know it is the stator? I bet he did not check with a DVA. Also if it is a Stator issue I would replace the trigger also if they are cheap enough probally around 100. I would do it my self. This guy is just guessing. Get a manual check all the ignition pieces with a meter and replace what is bad. this Motor may need a refresh in the ignition department then you will be good for years. IF you replace the stator, trigger, and rectifier your self it will be cheaper than letting that joker change your stator and having problems later becouse he didnt give it a good check.

 

[ugadawg187]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

So the motor should hit 5500 rpms? A bad trigger & stator could cause the motor to only hit 4000 rpm's at best? Im not sure if i can replace the stator & trigger myself cause of pulling the flywheel. I could screw up the timing when i pull it off correct? Also heres pic of the black/white wire that needs to be replaced cause the insulation is gone plus the wire is almost broken. That wire is coming from the trigger?

 

[ugadawg187]

Re: 1988 Mercury 45 hp classic 50 idling probs

Re: 1988 Mercury 45 hp classic 50 idling probs

Im going to buy a merc handbook for my motor but i hope you guys dont mind filling me in with the info until i get it in a week or so. So the motor wont idle but will run if you give it throttle & its sluggish getting up to speed but seems fine on top end but only reaching 3500-4000 rpms. Is WOT 5500? & could the carbs, stator, trigger be to blame???

 

[verado7]

Re: 1988 Mercury 45 hp classic 50 idling probs & only 4000 rpms at WOT

yes thats 1 of 4 trigger wires - and the motor rpm range is 5000 to 5500 rpm max . burnt trigger wire could be from a the igniton box ( faulty ) backfeeding voltage or arcing to ground .